Doing a little research on how to encourage the, yes the compost is a good start. They also like minimal soil disturbance, which I suspect is ideal management in an orchard. Based on my own experience here, you will also need to keep the soil evenly moist and preferable sheltered from direct sunlight with a mulch or plant cover.
My soils here dry out through most of the
yard each summer because I've refused to
water grass during our summer drought. Because of that, I've been spraying nematodes at the start of the wet season each year, but can't maintain a healthy population. Even the short time they survive in my yard makes a big difference in the number of
ants, grubs, and
fleas we have for the rest of the year. I will be so happy if I finally improve my soils
enough that I can stop spraying for these benefits. I'll know it's happened when fire ants stop coming back into the yard.
Edit: adding a link that does a very good job of explaining how beneficial nematodes work, without trying to
sell them.
https://garden.org/learn/articles/view/198/